Cathode ray tube envelope



Dem 1964 c. P. P'FLEEGER ETAL 3,161,314

CATHODE RAY TUBE ENVELOPE Filed Dec. 19. 1961 INVENTORS Cf/HELES PFL EEG 1? AND fax/Iv L WEBB J E- Airmen/5y United States Patent 3,161,314 CATHGDE RAY TUBE ENVELQPE Charles P. Pfieeger, Big Flats, and John L. Webb, 5112, Corning, N.Y., assignors to Corning Glass Works, Corning, N.Y., a corporation of New York Filed Dec. 19, 1961, Ser. No. 160,516 3 Claims. (Cl. 220-21) This invention relates to an improved envelope construction for cathode ray tubes.

It is an object of the invention to provide an envelope for use in conjunction with circular deflecting yokes which maximizes the amount of electron beam deflection attainable for a given tube length and at the same time gives the maximum envelope strength attainable in the yoke portion of the funnel consistent with this maximum deflect-ion.

Various forms have been proposed for the configuration of the yoke portions of television envelopes, which are those portions of the funnel located adjacent to the cylindrical neck which houses the electron gun assembly and in the general area of the deflecting yoke coils. As examples of those forms disclosed in the prior art which are closest to that of the present invention, reference is made to US. Patents 2,591,521 and 3,005,122, issued respectively to J. de Gier and J. C. Coleman et al. The former of these patents discloses a juncture between the yoke portion and the cylindrical neck which juncture is circular in external section and rectangular in internal section, while the latter discloses a yoke portion which has either a circular external section and a circular internal section modified by four spaced indentations (FIG. 7) or both internal and external sections in the general form of a rectangle having outwardly curving sides (FIG. 8).

The juncture between the neck and funnel disclosed in the De Gier patent is not a restriction on electron beam deflection in current cathode ray tubes, in which the electron beams are deflected through wide angles and impinge on substantially flat viewing screens. Present beam corrections result in generally parabolic electron paths, which cause restriction of the electron beam by the glass envelope to occur in the yoke portion of the funnel rather than the juncture between the neck and the yoke portion. In addition, the juncture of the De Gier patent has the disadvantage that due to the straight sides of its internal sections and the thinness of the glass at the corners of the rectangular sections, the yoke portion, because of both its geometry and the resultant cooling stresses, tends to be Weaker than may be desirable. The first-mentioned embodiment disclosed in the Coleman patent suffers disadvantage in that since. the internal section of the yoke portion is not similar to the shape of the viewing screen, there is a substantial part of the yoke portion which is neither traversed by the electron beam nor occupied by glass which would serve to strengthen the portion. In addition, weakness results from the fact that the internal section is not a continuous curve, and hence stresses tend to be distributed very unevenly. The second-mentioned embodiment of the Coleman patent is designed for use with a rectangular deflecting yoke, and although it has thp optimum internal section, it is weaker than it need be when used in conjunction with a circular deflecting yoke, since in such case there exists unused space between the circular deflecting yoke and the semi-rectangular yoke portion external surface. (The term semi-rectangular is used herein to refer to a section which approximates the form of a rectangle having each of its sides curved slightly outwardly and having rounded corners.)

It has been found advantageous to eliminate this lastmentioned disadvantage and to produce in a cathode ray tube envelope a yoke portion having an internal section in a semi-rectangular shape generally similar to that of the viewing area of the tube and having the advantages of strength inherent in a circular external section.

Accordingly, the present invention comprises a cathode ray tube envelope having such a yoke portion and illustrated in the accompanying drawing, in which:

FIGURE 1 is a side elevational view of a cathode ray tube utilizing the invention, and

FIGURE 2 is an enlarged section taken on line 2-2 of FIGURE 1.

All references in the drawings to sections of the illustrated cathode ray tube envelope are intended to refer to the intersections of the respective internal and external surfaces of the envelope with planes perpendicular to the axis of symmetry of the tube, that is, perpendicular to the direction of motion of the electron beam prior to deflection.

Referring to the drawing, the illustrated cathode ray tube envelope 10 comp-rises funnel portion 11, neck portion 12 and face plate 13. Neck portion 12 is in the form of a hollow right circular cylinder. The funnel 11 may have its sectional configuration in any form dictated by expediency. The yoke portion forming the transition between neck 12 and the main body of funnel 11 is circular in its external section and semi-rectangular in its internal section, as illustrated respectively by lines 14 and 15 of FIGURE 2. The semi-rectangular internal section varies in shape and dimensions to form a gradual transition from the circular internal section of neck 12 to the middle part of the yoke portion of the funnel, which has an internal section similar to the shape of the viewing surface of face plate 13, and on to the main body of funnel 11, which is of any conventional sectional configuration as dictated by considerations of space and strength. Throughout this transition area the external section is substantially circular and increases in diameter in the direction of face plate 13, as does the semi-rectangular internal section.

The illustrated configuration has been found to be optimum for use with presently available circular deflecting yokes, giving the benefit of the strength inherent in a circular external section and at the same time permitting the maximum possible deflection of the electron beam for any given tube length, since no space within the deflecting yoke remains unused.

If the additional strength provided by the present invention is not required, the advantages of the invention can be utilized to permit the tube to be made narrower in the yoke portion, thus permitting both the manufacture of lighter tubes and the utilization of lower voltages in the deflecting yoke coils.

We claim:

1. In a cathode ray tube envelope having a funnel portion, a cylindrical neck portion and a face portion with a viewing area defined by a continuous curve approximating the shape of a rectangle having each of its sides curved slightly outwardly and having rounded corners, the improvement which comprises a yoke portion forming a gradual transition increasing in size from said neck portion to said funnel portion and having a substantially circular external cross-section throughout and an internal cross-section forming a gradual transition from a circular cross-section at the juncture of said yoke portion and said neck portion to a cross-section in the central part of said yoke portion in the form of a continuous curve approximating the shape of a rectangle having each of its sides curved slightly outwardly and having rounded corners. I

2. The improvement according to claim 1 in which said internal cross-section of said yoke portion in the central part of said yoke portion is substantially geometrically similar to said curve defining said viewing area.

3. In a component for a cathode ray tube envelope,

which'component has a funnel portion and a cylindrical neck portion, the improvement which comprises ayokelportion forming a gradual transition increasing in size 7 c from said neck portion to said funnel portion and having a substantially circular external cross-section i'ncreasing in diameter from said neck portion to said funnel portion and having an internal cross section forming a gradual transition from a circular cross-section at the juncture of said yoke portion and said neck portion to a cross-section in the central part of said yoke portion in the form of a continuous curve approximating the shape of a rectangle I llavin'g each of its sides 'curved' s1ightlyoutward1y and hav- 'ing rounded corners;

References-Cited in the file of this patent UNITED STATES PATENTS 7 2,591,521 V De Gier 'Apr. 1, 1952 3,005,122 Colemarretal. Oct. 17, 1 961 V FOREIGN PATENTS m 820,181 Great Britain "Sept. 16, 1959 

3. IN A COMPONENT FOR A CATHODE RAY TUBE ENVELOPE WHICH COMPONENT HAS A FUNNEL PORTION AND A CYLINDRICAL NECK PORTION, THE IMPROVEMENT WHICH COMPRISES A YOKE PORTION FORMING A GRADUAL TRANSITION INCREASING IN SIZE FROM SAID NECK PORTION TO SAID FUNNEL PORTION AND HAVING A SUBSTANTIALLY CIRCULAR EXTERNAL CROSS-SECTION INCREASING IN DIAMETER FROM SAID NECK PORTION TO SAID FUNNEL PORTION AND HAVING AN INTERNAL CROSS-SECTION FORMING A GRADUAL TRANSITION FROM A CIRCULAR CROSS-SECTION AT THE JUNCTURE OF SAID YOKE PORTION AND SAID NECK PORTION TO A CROSS-SECTION IN THE CENTRAL PART OF SAID YOKE PORTION IN THE FORM OF A CONTINUOUS CURVE APPROXIMATELY THE SHAPE OF A RECTANGLE HAVING EACH OF ITS SIDES CURVED SLIGHTLY OUTWARDLY AND HAVING ROUNDED CORNERS. 